objects of study. The first half of his scientific career he dealt chiefly 

 with physiological problems, and in the latter half with those of 

 comparative anatomy. He added enormously to his great Museum of 

 Human and Comparative Anatomy in Berlin. 



Regarding the minute structure of glands, his monograph De 

 Gland, secern. Structurd penitiori (Lip. 1830) marks an epoch. He 

 supported the view of E. H. Weber that the gland acini are the direct 

 continuation of the ducts, and he showed the exact relation of the 

 capillaries to the acini themselves. As we have already stated, the 

 first researches were those of Malpighi published in 1665. Ruysch 

 attributed great importance to the blood vessels of the acini, and 

 Haller endorsed his view. Mascagni and Cruickshank had shown that 

 the secreting canals in the mammary gland commenced in cells, and 

 E. H. Weber had shown that the same was the case in salivary glands 

 and pancreas of birds. Mttller's monograph ranges over all the glands, 

 and deals with those both of vertebrate and invertebrate animals. He 

 shows how the acini are closed save where they open into a duct, 

 and how the blood-vessels ramify outside the membrane of the acini. 

 An abridgment of this work was published in 1839, The Intimate 

 Structure of Secreting-glands, by Samuel Solly. On plate iii., Fig. 8, 

 we have one of the solitary follicles, from the mucous membrane of 

 the rectum represented as containing a cavity opening by a constricted 

 orifice. In embryology his name is associated with the " Miillerian 

 duct." " Richard Owen and Muller must be regarded as the founders 

 of modern comparative anatomy, which largely depends on the study 

 of embryology, and on the investigation of simpler forms." His chief 

 work in this respect, Vergleichende Anatomie d. Myxinoiden, is and 

 must remain a classic. While in Bonn he discovered and wrote upon 

 certain of the lymph hearts in the frog and tortoise : On the existence 

 of four distinct Hearts, having regular pulsations, connected with the 

 Lymphatic System in certain Amphibious Animals. (Phil. Trans., 

 1833.) It was Marshall Hall's Essay on Circulation of the Blood, 

 1831, which led Muller to discover the lymph hearts in 1832. 



As regards his influence on physiological doctrine, he is the 

 representative of " Vitalismus." There was a certain mystic element 

 in Miiller's nature, and he wrote a remarkable work on apparitions, 

 Phantastische Gesichts Erscheinunyen (Coblenz 1826). While in Bonn 

 he used the frog to test the truth of Bell's law. 



" The happy thought at length occurred to me of performing the experiment on frogs. 

 The result was most satisfactory. The experiments are so easily performed, so certain 

 and conclusive, that every one can now very readily convince himself of one of the most 

 important truths of physiology. . . . It is quite impossible to excite muscular 

 contractions in frogs by irritating mechanically the posterior roots of the spinal nerves ; 

 while, on the other hand, the slightest irritation of the anterior roots immediately gives 

 rise to strong action of the muscles. . . . The application of galvanism to the 

 anterior roots of the spinal nerves, after their connection with the cord is divided, 



